Composite material with conductive structures of random size, shape, orientation, or location
A composite material with at least one of a negative effective permittivity and a negative effective permeability for incident radiation of at least one wavelength is described. The composite material comprises conductive structures that are substantially random with respect to at least one of size, shape, orientation, and location.
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This invention has been made with government support under Contract No. HR0011-05-3-0002, awarded by Defense Advanced Research Projects Agency. The government has certain rights in the invention.
FIELDThis patent specification relates generally to the propagation of electromagnetic radiation and, more particularly, to composite materials capable of exhibiting negative effective permeability and/or negative effective permittivity with respect to incident electromagnetic radiation.
BACKGROUNDSubstantial attention has been directed in recent years toward composite materials capable of exhibiting negative effective permeability and/or negative effective permittivity with respect to incident electromagnetic radiation. Such materials, often interchangeably termed artificial materials or metamaterials, generally comprise periodic arrays of electromagnetically resonant cells that are of substantially small dimension (e.g., 20% or less) compared to the wavelength of the incident radiation. Although the individual response of any particular cell to an incident wavefront can be quite complicated, the aggregate response the resonant cells can be described macroscopically, as if the composite material were a continuous material, except that the permeability term is replaced by an effective permeability and the permittivity term is replaced by an effective permittivity. However, unlike continuous materials, the resonant cells have structures that can be manipulated to vary their magnetic and electrical properties, such that different ranges of effective permeability and/or effective permittivity can be achieved across various useful radiation wavelengths.
Of particular appeal are so-called negative index materials, often interchangeably termed left-handed materials or negatively refractive materials, in which the effective permeability and effective permittivity are simultaneously negative for one or more wavelengths depending on the size, structure, and arrangement of the resonant cells. Potential industrial applicabilities for negative-index materials include so-called superlenses having the ability to image far below the diffraction limit to λ/6 and beyond, new designs for airborne radar, high resolution nuclear magnetic resonance (NMR) systems for medical imaging, and microwave lenses.
One issue that arises in the realization of useful devices from such composite materials, including negative index materials, relates to the practical manufacturability of devices when precise dimensioning and positioning of the resonant cells is required, especially for devices operable at optical frequencies requiring very small resonator dimensions. Another issue relates to achieving isotropic behavior in two or three dimensions, such isotropy often being desirable for many practical applications. Another issue relates to substantial losses experienced by the incident electromagnetic signal when propagating through the composite material. Other issues arise as would be apparent to one skilled in the art upon reading the present disclosure.
SUMMARYIn accordance with an embodiment, a composite material with at least one of a negative effective permittivity and a negative effective permeability for incident radiation of at least one wavelength is provided. The composite material comprises conductive structures that are substantially random with respect to at least one of size, shape, orientation, and location. The conductive structures have minor dimensions less than about one fiftieth of the incident radiation wavelength.
Also provided is a composite material with at least one of a negative effective permittivity and a negative effective permeability for incident radiation of at least one wavelength, comprising a matrix material and a plurality of conductive structures disposed in the matrix material. The conductive structures are substantially random with respect to at least one of size, shape, orientation, and location and have minor dimensions substantially smaller than the incident radiation wavelength. The matrix material exhibits gain in an amplification band that includes the incident radiation wavelength.
Also provided is a method for propagating incident electromagnetic radiation at an operating wavelength, comprising placing a composite material in the path of the incident electromagnetic radiation, the composite material having at least one of a negative effective permittivity and a negative effective permeability at the operating wavelength. The composite material comprises conductive structures that are substantially random with respect to at least one of size, shape, orientation, and location and have minor dimensions less than about one-fiftieth of the operating wavelength.
Also provided is a method for propagating incident electromagnetic radiation at an operating wavelength, comprising placing a composite material in the path of the incident electromagnetic radiation, the composite material having at least one of a negative effective permittivity and a negative effective permeability at the operating wavelength. The composite material comprises a plurality of conductive structures disposed in a matrix material that exhibits gain at the operating wavelength. The conductive structures are substantially random with respect to at least one of size, shape, orientation, and location and have minor dimensions substantially smaller than the operating wavelength.
Also provided is a device for propagating incident radiation at an operating wavelength, comprising a matrix material and a plurality of conductive structures disposed in the matrix material. The conductive structures are substantially random with respect to at least one of size, shape, orientation, and location and have minor dimensions substantially smaller than the incident radiation wavelength such that at least one of a negative effective permittivity and a negative effective permeability are exhibited at the operating wavelength. The device further comprises means disposed in the matrix material for providing gain at the operating wavelength. The device further comprises means for powering the gain providing means.
According to an embodiment, the conductive structures 104 have minor dimensions that are less that about 1/50 of the wavelength for which the negative effective permittivity and/or negative effective permeability is desired, termed herein the operating wavelength. By way of example and not by way of limitation, for an operating wavelength of 600 nm in the optical range, the minor dimensions should be less than about 12 nm. For an operating wavelength of 1.55 μm in the near infrared range, the minor dimensions should be less than about 31 nm. For an operating wavelength of 10 μm in the far infrared range, the minor dimensions should be less than about 200 nm. For an operating wavelength of 1 mm in the microwave range, the minor dimensions should be less than about 20 μm. For an operating wavelength of 10 cm in the microwave range, the minor dimensions should be less than about 2 mm.
According to another embodiment, the conductive structures 104 have minor dimensions that are less that about 1/100 of the operating wavelength. According to another embodiment, the conductive structures 104 have minor dimensions that are less that about 1/1000 of the operating wavelength. For one embodiment, aspect ratios of the conductive structures 104 can range from 10:1 to 20:1. For another embodiment, aspect ratios of the conductive structures 104 can range from 1:1 (e.g., for spheres) to 20:1. For yet another embodiment, aspect ratios of the conductive structures 104 can range from 1:1 to 100:1. For still another embodiment, aspect ratios of the conductive structures 104 can range from 1:1 to more than 100:1.
According to one embodiment, between 25 percent and 75 percent of the conductive structures are elongate with aspect ratios greater than about 5:1. According to another embodiment, between 0 percent and 100 percent of the conductive structures are elongate with aspect ratios greater than about 5:1.
Preferably, the conductive structures 104 are substantially random with respect to at least one of size, shape, orientation, and location. In the particular example of
In one embodiment, the conductive structures 104 comprise one or more metals such as silver, gold, platinum, copper, cobalt, nickel, or aluminum. It is to be appreciated, however, that the composition of conductive structures 104 is not limited to metals, but can generally include any material capable of supporting plasmon and/or polariton resonance through the effects of surface charge density variations at the frequency for which the negative effective permittivity and/or negative effective permeability is desired. Thus, for example, for optical, near-infrared, and far-infrared frequencies, the conductive structures 104 can comprise materials such as metallic carbon nanotubes, aluminum oxide, and doped semiconductor materials such as InP. The conductive structures 104 can optionally comprise multiple layers of material, such as metallic layers interleaved with semiconductor or dielectric layers.
The matrix material 103 is preferably non-conducting and relatively transparent at the operating wavelength. The matrix material 103 should also be capable of physically supporting and/or suspending the conductive structures 104 therein to have the required locations or statistical distribution of locations, as well as the required orientations or statistical distribution of orientations. Where static (i.e., time-invariant) locations and orientations are desired, the matrix material 103 should comprise a solid or semi-solid material. Where time-varying locations and orientations are permissible, the matrix material may comprise a liquid or semi-liquid that maintains the conductive structures 104 in suspension. By way of non-limiting example, for operating wavelengths in the optical or near-infrared range, the matrix material 103 may comprise SiO2 or an undoped semiconductor material. For operating wavelengths in the far-infrared range, the matrix material 103 may comprise NaCl or ZnSe. For operating wavelengths in the microwave range, suitable matrix materials may comprise polystyrene foam.
Generally speaking, the desired negative effective permittivity and/or negative effective permeability are exhibited at operating wavelengths and propagation directions for which a sufficiently large sub-population of the conductive structures 104 collectively bring about the required plasmon and/or polariton resonance conditions. Thus, for the example of
Generally speaking, the presence of linear conductive paths, as may be provided by the elongate structures described herein, serves to facilitate or strengthen a negative effective permittivity of the composite material, especially for radiation propagating in directions at least roughly perpendicular to the direction of the linear currents. Generally speaking, the presence of circular or ring-like conductive paths, as may be provided by the spheroidal structures described herein as well as many elongate structures, serves to facilitate or strengthen a negative effective permeability of the composite material, especially for radiation propagating in directions at least roughly parallel to the planes of the circular or ring-like currents.
It is to be appreciated, however, that a variety of different gain materials or mechanisms can be used to introduce the desired gain into the propagating radiation without departing from the scope of the present teachings. By way of example, for one embodiment in which the operating wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range, the matrix material can be doped with rare earth ions such erbium, yttrium, neodymium, or praseodymium ions that provide gain when optically pumped. In another example, the composite material 1303 further comprises a quantum well gain material having an amplification band that includes the operating wavelength, the quantum well gain material being conformally grown around each of said conductive structures 1304. In yet another example, for operating wavelengths in the microwave frequency range, the composite material can comprise tiny optically powered integrated circuit microwave amplifier chips distributed throughout, the amplifier chips comprising photodiodes that convert pump radiation into electrical power, the electrical power being used to drive the amplifier circuitry that amplifies the propagating microwave radiation.
Although the air or dielectric holes 1406 are subwavelength structures, they will generally be substantially larger than the minor dimensions of the conductive structures 1404. By way of example, whereas the minor dimensions of the conductive structures 1404 will often be on the order of λ/50 or less in size, the air or dielectric holes 1406 will be on the order of λ/3 in diameter. Optionally, a defect waveguide 1408 is formed by omitted holes or other variations to the periodic pattern, as illustrated in
Whereas many alterations and modifications of the embodiments will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. By way of example, while some embodiments supra are described in the context of negative-index materials, the features and advantages of the embodiments are readily applicable in the context of so-called indefinite materials in which the permeability and permittivity are of opposite signs. By way of further example, a randomized or partially randomized composite material similar to that of some embodiments supra can be implemented as a portion of a larger composite material having other non-random components.
By way of still further example, various parameters such as pump energies, pump frequencies, per-side dimensions, and conductive structure directionalities can be modulated in real-time or near-real time for achieving any of a variety of different useful results. By way of even further example, the air or dielectric holes of a photonic crystal structure formed from a first type of composite material having a first type of conductive structures can be occupied instead by a second type of composite material having a second type of conductive structures. Thus, reference to the details of the described embodiments are not intended to limit their scope.
Claims
1. A composite material with at least one of a negative effective permittivity and a negative effective permeability for incident radiation of at least one wavelength comprising conductive structures that are substantially random with respect to at least one of size, shape, orientation, and location and that have a minor dimension less than about one fiftieth of said incident radiation wavelength, wherein said incident radiation wavelength corresponding to one of an optical, near-infrared, and far infrared frequency range, said composite material further comprising a quantum well gain material having an amplification band that includes said incident radiation wavelength, said quantum well gain material being conformally grown around each of said conductive structures.
2. The composite material of claim 1, wherein said minor dimension is less than about 1/100 of said incident radiation wavelength.
3. The composite material of claim 1, wherein said minor dimension is less than about 1/1000 of said incident radiation wavelength.
4. The composite material of claim 1, wherein said conductive structures have substantially random orientations with a statistical preference toward a first orientation at least roughly perpendicular to a direction of propagation of radiation at said incident radiation wavelength, and wherein at least 50% of said conductive structures are oriented within 45 degrees of said first orientation.
5. The composite material of claim 1, wherein said incident radiation wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range and said conductive structures comprise nanostructures selected from the group consisting of metallic carbon nanotubes, nanocylinders, nanorods, nanospheres, elongate nanostructures, swiss rolls, and split-ring resonators.
6. The composite material of claim 1, wherein between 25 percent and 75 percent of said conductive structures are elongate with aspect ratios greater than about 5:1.
7. The composite material of claim 1, wherein said conductive structures are distributed in a matrix material, wherein said matrix material and said conductive structures therein are formed into one of a waveguiding structure and a photonic crystal structure having a photonic bandgap that includes said incident radiation wavelength.
8. A composite material with at least one of a negative effective permittivity and a negative effective permeability for incident radiation of at least one wavelength, comprising:
- a matrix material; and
- a plurality of conductive structures disposed in said matrix material, said conductive structures being substantially random with respect to at least one of size, shape, orientation, and location and having a minor dimension substantially smaller than said incident radiation wavelength;
- wherein said matrix material exhibits gain in an amplification band that includes said incident radiation wavelength.
9. The composite material of claim 8, wherein said incident radiation wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range, and wherein said matrix material comprises at least one of a rare earth ion doped material and a quantum dot gain material, said quantum dot gain material comprising quantum dots having amplification bands that include said incident radiation wavelength.
10. The composite material of claim 8, wherein said incident radiation wavelength corresponds to a microwave frequency range, and wherein said matrix material comprises optically powered integrated circuit microwave amplifiers distributed in the matrix material.
11. The composite material of claim 8, wherein (A) said incident radiation wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range and said conductive structures comprise nanostructures selected from the group consisting of metallic carbon nanotubes, nanocylinders, nanorods, nanospheres, elongate nanostructures, swiss rolls, and split-ring resonators, or (B) said incident radiation wavelength corresponds to a microwave frequency range and said conductive structures comprise metallic structures selected from the group consisting of cylinders, rods, spheres, elongate structures, swiss rolls, and split-ring resonators.
12. The composite material of claim 8, wherein said minor dimension is less than about one fiftieth of said incident radiation wavelength.
13. The composite material of claim 8, wherein said matrix material and said conductive structures therein are formed into a photonic crystal structure having a photonic bandgap that includes said incident radiation wavelength, said photonic crystal structure defining a defect waveguide propagating radiation at said incident radiation wavelength therealong.
14. A method for propagating incident electromagnetic radiation at an operating wavelength, comprising placing a composite material in the path of the incident electromagnetic radiation, the composite material having at least one of a negative effective permittivity and a negative effective permeability at said operating wavelength, the composite material comprising conductive structures that are substantially random with respect to at least one of size, shape, orientation, and location and that have a minor dimension less than about one-fiftieth of said operating wavelength, wherein said operating wavelength corresponding to one of an optical, near-infrared, and far infrared frequency rang, said composite material further comprising a quantum well gain material having an amplification band that includes said operating wavelength, said quantum well gain material being conformally grown around each of said conductive structures.
15. The method of claim 14, wherein said minor dimension is less than about 1/100 of said operating wavelength.
16. The method of claim 14, wherein said minor dimension is less than about 1/1000 of said operating wavelength.
17. The method of claim 14, wherein said conductive structures have substantially random orientations with a statistical preference toward a first orientation at least roughly perpendicular to a direction of propagation of the electromagnetic radiation, and wherein at least 50% of said conductive structures are oriented within 45 degrees of said first orientation.
18. The method of claim 14, wherein said operating wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range and said conductive structures comprise nanostructures selected from the group consisting of metallic carbon nanotubes, metallic nanocylinders, metallic nanorods, metallic nanospheres, elongate metallic nanostructures, metallic swiss rolls, and metallic split-ring resonators.
19. The method of claim 14, wherein between 25 percent and 75 percent of said conductive structures are elongate with aspect ratios greater than about 5:1.
20. The method of claim 14, wherein said conductive structures are distributed in a matrix material, wherein said matrix material and said conductive structures therein are formed into one of (A) a waveguiding structure, and (B) a photonic crystal structure having a photonic bandgap that includes said operating wavelength.
21. A method for propagating incident electromagnetic radiation at an operating wavelength, comprising placing a composite material in the path of the incident electromagnetic radiation, the composite material having at least one of a negative effective permittivity and a negative effective permeability at the operating wavelength, the composite material comprising a plurality of conductive structures disposed in a matrix material that exhibits gain at said operating wavelength, said conductive structures being substantially random with respect to at least one of size, shape, orientation, and location and having a minor dimension substantially smaller than said operating wavelength.
22. The method of claim 21, wherein said operating wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range, and wherein said matrix material comprises at least one of a rare earth ion doped material and a quantum dot gain material, said quantum dot gain material comprising quantum dots having amplification bands that include said operating wavelength, and wherein the method further comprises providing pump radiation to the matrix material.
23. The method of claim 21, wherein said operating wavelength corresponds to a microwave frequency range, and wherein said matrix material comprises a plurality of optically powered integrated circuit microwave amplifiers, and wherein the method further comprises providing pump radiation to the matrix material.
24. The method of claim 21, wherein (A) said operating wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range and said conductive structures comprise nanostructures selected from the group consisting of metallic carbon nanotubes, metallic nanocylinders, metallic nanorods, metallic nanospheres, elongate metallic nanostructures, metallic swiss rolls, and metallic split-ring resonators, or (B) said operating wavelength corresponds to a microwave frequency range and said conductive structures comprise metallic structures selected from the group consisting of cylinders, rods, spheres, elongate structures, swiss rolls, and split-ring resonators.
25. The method of claim 21, wherein said minor dimension is less than about 1/100 of said operating wavelength.
26. The method of claim 21, wherein said matrix material and said conductive structures therein are formed into a photonic crystal structure having a photonic bandgap that includes said operating wavelength, said photonic crystal structure defining a defect waveguide propagating said electromagnetic radiation at said operating wavelength therealong.
27. A device fin propagating incident radiation at an operating wavelength, comprising:
- a matrix material;
- a plurality of conductive structures disposed in said matrix material, said conductive structures being substantially random with respect to at least one of size, shape, orientation, and location and having a minor dimension substantially smaller than said incident radiation wavelength such that at least one of a negative effective permittivity and a negative effective permeability are exhibited at said operating wavelength;
- means disposed in said matrix material for providing gain at said operating wavelength; and
- means for powering said means for providing gain.
28. The device of claim 27, wherein said operating wavelength corresponds to one of an optical, near-infrared, and far infrared frequency range, wherein said means for powering comprises a pump radiation source configured to project pump radiation toward said matrix material, and wherein said means for providing gain comprises one of (A) a rare earth ion doped material, (B) a plurality of quantum dots having amplification bands that include said operating wavelength, and (C) a quantum well gain material conformally grown around each of said conductive structures.
29. The device of claim 27, wherein said operating wavelength corresponds to a microwave frequency range, wherein said means for powering comprises a pump radiation source configured to project optical pump radiation toward said matrix material, and wherein said means for providing gain comprises a plurality of optically powered integrated circuit microwave amplifiers dispersed throughout said matrix material.
30. The device of claim 27, wherein said minor dimension is less than about one fiftieth of said operating wavelength.
6465132 | October 15, 2002 | Jin |
6536106 | March 25, 2003 | Jackson et al. |
6741019 | May 25, 2004 | Filas et al. |
6791432 | September 14, 2004 | Smith et al. |
6977767 | December 20, 2005 | Sarychev et al. |
7106918 | September 12, 2006 | Bita et al. |
7474823 | January 6, 2009 | Wang et al. |
7482727 | January 27, 2009 | Bratkovski et al. |
7492329 | February 17, 2009 | Wang et al. |
7593170 | September 22, 2009 | Wu et al. |
20030042487 | March 6, 2003 | Sarychev et al. |
20050161630 | July 28, 2005 | Chui et al. |
20050221128 | October 6, 2005 | Kochergin |
20060003152 | January 5, 2006 | Youngs |
20060131695 | June 22, 2006 | Kuekes et al. |
20060152430 | July 13, 2006 | Seddon et al. |
WO 01/71774 | September 2001 | WO |
WO 03075291 | September 2003 | WO |
WO 2004/034504 | April 2004 | WO |
WO 2005/031864 | April 2005 | WO |
- R A Shelby et al-“Microwave transmission through a two-dimensional, isotropic, left-handed metamaterial”-Applied Physics Letters vol. 78 No. 4-Jan. 22, 2001-pp. 489-491.
- Yannopapas, Vassilios, et. al., “Negative Refractive Index Metamaterials From Inherently Non-Magnetic Materials . . . ,” J. Phys.:Condens. Matter 17 3717-3734 (2005).
- Holloway, C. L., “A Double-Negative (DNG) Composite Medium Composed of Magnetodielectric . . . ,” IEEE. Trans. Ant. & Prop., vol. 51, No. 10, 2596-2603 (Oct. 2003).
- Zharov, A. A., et. al., “Suppression of Left-Handed Properties in Disordered Metamaterials,” J. Appl. Phys. 97, 113906 (2005).
- Felbacq, D., “Negative Refraction in Periodic and Random Photonic Crystals,” New J. Physics 7 (2005) 159 (www.njp.org).
- Zharov, A. A., et. al., “Birefringent Left-Handed Metamaterials and Perfect Lenses for Vectorial Fields,” New J. Physics 7 (2005) 220 (www.njp.org).
- Podolskiy, V., et. al., “Plasmon Modes and Negative Refraction in Metal Nanowire Composites,” Optics Express, vol. 11, No. 7 735-745 (Apr. 7, 2003).
- Hangarter, C., et. al., “Magnetic Alignment of Nanowires,” Chem. Mater., vol. 17, No. 6, 1320-1324 (2005).
- Kalaugher, L., “Nickel Nanowire Caps Lead to Manipulation,” News—www.nanotechweb.org (Feb. 3, 2004).
- Engheta, N., “Metamaterials with Negative Permittivity and Permeability: Background, Salient Features . . . ,” IEEE MTT-S Int. Microwave Symp. Dig. 2003, vol. 1, 187-190 (2003).
Type: Grant
Filed: Nov 30, 2005
Date of Patent: Nov 30, 2010
Patent Publication Number: 20070120114
Assignee: Hewlett-Packard Development Company, L.P. (Houston, TX)
Inventors: Shih-Yuan Wang (Palo Alto, CA), Alexandre Bratkovski (Palo Alto, CA)
Primary Examiner: Anh Phung
Assistant Examiner: Michael Lulis
Application Number: 11/290,685
International Classification: H01L 33/58 (20100101); H01L 31/0232 (20100101);